The Papal Swiss Guard was founded in 1506. It is today largely
ceremonial, but like the Guards in London they are a fully
operational modern military force. When in ceremonial 16th
century uniform, they keep their firearms in guard boxes nearby.
The Papal Guard are the only mercenary unit permitted under Swiss
law since 1859, and are the last of a long tradition of a million
mercenaries in the world's armies. The Guard today consists of 5
officers, 25 NCOs and 70 halberdiers.
You can see a photo of recruits swearing in on
the Guards flag at www.christusrex.org.
I don't know when the flag was instituted, or how it has evolved,
but it represents the 18th century tradition of Swiss mercenary
flags. It consists of a white cross "traversante"
(extending to the edges, unlike the modern short Swiss cross)
which conveniently divides the flag into brightly coloured
quarters. The first and fourth quarters are identical and consist
of the Pope's arms on a red field. Presumably these change on the
Swiss Guards' flag with every new pope. The second and third
quarters are also identical, consisting of five horizontal
stripes -- blue-yellow-red-yellow-blue. (These are the colours of
the Guards' Renaissance-style uniform, which incidentally dates
from 1915, and was not designed by Michelangelo as the popular
myth would have us believe.) The central device on the white
cross is probably the arms of the colonel of the regiment, or
those of the Pfyffer d'Altishofen family which made the colonelcy
hereditary from 1652 to 1847. I'm not sure what the rules are for
changing the central coat of arms.
The colour photo represents the annual swearing in of recruits on
6 May (and the Guard's principal ceremonial event). This is the
anniversary of the 1527 sack of Rome when the 200-strong Guard
defended Pope Clement VII against a Spanish-German army of
22,000. 147 were killed (including the Captain Kaspar Roist of
Zurich), and the survivors took the Pope to Castel San Angelo
where they held out for a month before negiotiating a surrender.
Ironically Zurich was in the throws of the Reformation and had
recalled the Captain and his fellow Zurichers. They decided to
wait until the storm blew over, and paid for it with their lives.
T.F. Mills, 6 May 1998

The following is paraphrased and condensed from the article on
the Swiss Guards in the New Catholic Encyclopedia:

"From the time of the Middle Ages, Swiss pikemen fought as
mercenaries in the armies of many European states under treaties
with the various Swiss cantons. Among the most famous of
these were the Garde Suisse of the French monarchy.
Swiss soldiers served the armies of the Papacy from the late
1300s onward, but only during the reign of Julius II (1503-13)
was action taken to establish an organized unit of Swiss Guards
directly under the Pope. In 1505, pursuant to a treaty was
signed between Pope Julius II and the cantons of Zurich and
Lucerne, Julius requested that the two cantons send 200 soldiers
to Rome under the command of Peter von Hertenstein as condottiere
and Caspar von Silenen as captain. They arrived on January
21, 1506, and were taken into service with a papal blessing in
St. Peter's Square. That event is considered to be the date
of establishment of the Vatican's corps of Swiss Guards, the
"Cohors pedestris Helvetiorum a sacra custodia
Pontificis." This unit is the only modern survival of
the Swiss mercenary tradition, as the Swiss Constitution of 1874
prohibits the enlistment of Swiss citizens in the forces of
foreign powers with the exception of the Holy See.Joe McMillan , 28 February 2000

Quoting from The Banner of the Papal Swiss Guard by Walter
Angst in The Flag Bulletin, 187, May-June 1999

"only unmarried Swiss males of the Catholic faith -
historically, mainly from the four original Swiss cantons (Uri,
Schwyz, Unterwalden, Luzern) and Valais - are eligible for
serviece. Moreover, they must all be between 19 and 30
years of age, at least 174 cm tall and must have fulfilled their
basic military training in the Swiss Army. They are
privately contracted for this special Foreign Service for at
least two years. No official is openly involved in the
process, but usually the discreet services of some parish priests
are used. Guard duty includes the bodyguard for the
pontiff, the watch at the entrances to the city, the ceremonial
honor guard, security at many religious and diplomatic functions,
as well as information, surveillance, and similar service. The
commander of the Swiss Guard is always a colonel. He
belongs to the "pontifical family," holding the rank of
a "Chamberlain of His Holiness." The pope alone
appoints the commander. At present, the colonel commands a
lieutenant colonel, a guard chaplain, a major, a captain, a
master sergeant, four sergeants, 10 corporals, 10 vice-corporals,
and 70 halberdiers. This makes up the Guard of 100 men, although
in 1971 this force had dwindled to only 40 members. By law
the Guard can be composed of at most 100 volunteers; hence it is
called Hundertschweizer - (one hundred Swiss.)
"Unlike the regiments of the former military Foreigh Service
(which remained at times under the laws of the Swiss
Confederation), the Swiss Guard is under the pope who, throughthe
secretary of state of the Vatican, exercises far-reaching
jurisdiction over his 100 Swiss. The Guards must live
inside the walled city of the Vatican and they are considered
citizens of the Vatican State during their years of active
service. Since the Second Vatican Council, their famed
steel breast-armor is normally worn only on one special
ceremonial occassion - the yearly swearing-in ceremony of new
Guards, which takes place on 6 May."

The Flag Bulletin shows also the current flag of the Swiss guard,
divided into Four quarters by the Swiss cross. This flag
changes with every pope and with the commander of the Swiss
Guard. Therefore, the arms of Pope John Paul II in the
first quarter on a red background, horizontal stripes of blue,
yellow, red, yellow and blue in the second quarter, horizontal
stripes of red, yellow, blue, yellow and red in the third quarter
and the arms of Pope Julius II are in the fourth quarter on a red
background and centered on the cross the arms of the current
commander withing a green wreath.
Angst quotes 189 Swiss Guards who were at the 1527 sacking of
Rome, of which 147 perished. When the Germans invaded Rome
in 1944, the Swiss Guard stationed themselves in military grey
uniform, behind machine guns and mortars just in case.Phil Nelson , 29 February 2000

Above is an image of the Swiss Guard flag, . The flag is
2 meters square or a bit larger. The gray area on the
center inside the wreath is where the commander's arms are shown,
placed on a background of the colors of his native canton.Joe McMillan, 29 February 2000

Looking at the Swiss Guards flag as illustrated above, and
comparing it with the text, I see that according to the text the
arms in the first and fourth quarters are the same. However, in
your illustration, the arms in the first quarter are those of
John Paul II, while those in the fourth quarter show a tree.
Also, there is mention of a coat of arms in the centre (which is
shown in the photograph of guardsmen swearing allegiance), but
there's just a grey centre to the wreath in the illustration.Mike Oettle, 19 December 2001

The difference with the photo, as far as I can tell, is in the
Coat of Arms on the center of the cross and the size of the
achievements in the first and fourth quarters. The Coat of
Arms in the fourth quarter is not visible in the photo at the
link, except for the tiara and keys, and is therefore not
inconsistent with the image. As to the gray area on the
center, note what Phil Nelson wrote above: "This flag
changes with every pope and with the commander of the Swiss Guard
... centered on the cross the arms of the current commander
withing a green wreath" and my note: "The gray
area on the center inside the wreath is where the commander's
arms are shown, placed on a background of the colors of his
native canton."
The arms of Pope John Paul II in the first quarter on a red
background ... and the arms of Pope Julius II are in the fourth
quarter on a red background."Joe McMillan, 19 December 2001

Recently I ran across a website with some excellent photos of Swiss Guard
flags, including the most recent, at www.schweizergarde.info.
A PDF of the definitive Swiss Guard history, which contains
information on the history of the Guards' flags, is also
available there through a link: Paul Krieg, "Die Schweizergarde in Rom," p. 446-449. He states
that the current Guards' flag design dates from the tenure of
commander Jules Repond (1910- 1921).Rev. William M. Becker, 20 April 2005

This design exists since the early 20th cent. Above is a
tamplate with voided papal and commander arms, plus the Pope
Julius II's arms on the lower fly.
António Martins-Tuválkin, 7 June 2005

Considering only those Colonels after 1905 (when the current
Vatican Swiss Guard flag pattern was designed) and the popes from
the same period, we can list all flags that (theoretically)
existed:.

1905-1910
flag has never existed.

1910-1914
flag has never existed too. Pius X had completely
rejected the flag draft. Repond presented the draft of
the new flag design already in the year1912 . The pope
Pius X was not open to the new ideas. [Note:
that is not correct according to Rev. William M.
Becker, STD. - see below)
So the first use of the current pattern was 1914, not
1905.

1997-1998It is possible that Estermann was not represented by a
flag with his Coat of Arms since he served as commander for less
than one day. He was appointed 4 May 1998, and murdered by one of
his men a few hours later New recruits were to be sworn in on 6
May 1998 in the famous flag ceremony (the anniversary of the sack
of Rome in 1527 when 147 Swiss Guards died protecting Pope
Clement VII), and Estermann had been acting commander since
October 1997 when his predecessor resigned, so it is also
possible that a new flag was ready for 6 May, or even unveiled on
4 May.T.F. Mills, 9 June 2005

I believe there is an error in António Martins-Tuválkin
contribution inSwiss Guard flag pages regarding the
first version of their current flag design. António Martins-Tuválkin states that Pope Pius X
opposed the new (current) design sponsored by Commander Jules
Repond, and would not authorize it. But according to my sources,
that is not correct. The current version of the Swiss Guard flag
was approved in the last year of the pontificate of Pius X,
namely on November 1, 1913, by the Secretariat of State. It was
designed by Robert Durrer, a Swiss archivist, and sponsored by
Commander Jules Repond. The flag was produced by a
Swiss convent, and was blessed by Pius X on May 5, 1914, in time
for use at the traditional swearing-in of new recruits the next
day. Pius died a few months later. (Cf. Robert Walpen, La Guardia
Svizzera Pontificia. Acriter et fideliter. Coraggio e
fedeltà. Second Edition. Locarno, Switzerland:
Armando Dadò, 2005, p. 112-114. Walpen reproduces
Durrer's original sketch of the flag, and the note authorizing
its use from the Secretariat of State.)
Here is an actual photo of
this first version of the current Swiss Guard flag, from the
pontificate of Pius X. It was published in: "Die
neue Fahne der Schweizergarde," Archives Héraldiques
Suisses / Schweizerisches Archiv für Heraldik, vol. 28, no. 4
(Zürich: Imprimérie Schulthess & Co., 1914), p. 205-206
& Plate 5.
Also, here is a photo of
the Swiss Guards flag from the reign of Benedict XV, who followed
Pius X, appeared in L'Illustrazione Vaticana, no. 11/1932
(attached). Benedict's arms were simply painted over
those of Pius X, which was a common practice in past
centuries. (cf. Vincenz
Oertle. "' aux couleurs du pape régnant'
 Die Fahne der Päpstlichen Schweizergarde,"
Zeitschrift für Heereskunde, number 419 [January/March 2006], p.
1-6.)
The photos of the Repond/Durrer design used under Pius X and Benedict XVI were
previously posted at www.schweizergarde.info;
but that site is currently offline for some reason.Rev. William M. Becker, STD, 13 July 2007

National Bank of Austria listing some commemorative
Euro issues. One of the coins is "EUR 2 VATICAN 2008"
with the following quote:
"Feature: 5th centenary of the Swiss Pontifical Guard
Description: The coin features a Swiss guard taking the solemn
oath on the Swiss Guard flag. The inscription "GUARDIA
SVIZZERA PONTIFICIA" surrounds the guard, forming a
semi-circle which is complemented under the flag by the name of
the issuing state "CITTÁ DEL VATICANO". The year 1506
appears on the left side, above the signature of the engraver
"O. ROSSI" along the pole of the flag. The year 2006
appears on the upper right side, above the mint mark
"R". The twelve stars of the European flag are depicted
on the outer ring.
Issuing volume: a maximum of 100,000 coins
Issuing date: November 2006
Edge lettering: 2* repeated six times, alternately upright and
inverted."Jan Mertens, 17 August 2008

The Swiss Guard will replace on 6 May 2013 (Sacco di Roma) a new flag. The
flag should show the new coat of arms of the Pope Francis and the coat of arms
of the Swiss commander Daniel Anrig. Here a proposal.Jens Pattke,
18 March 2013